Upgrade to LevelDB 1.21 or 1.22

[rvagg]

This just in on the LevelDB mailing list that I thought might be interesting for folks here.

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From: Victor Costan

Hi everyone!

For planning purposes, please know that the upcoming leveldb release (1.21) will introduce significant changes to the build process. As always, the API will remain backwards-compatible.
The build system will be switched to CMake.
Configuration macros will change to reflect CMake conventions. (example: HAVE_SNAPPY instead of SNAPPY)
Building the library will require C++11 support.
A new optional dependency will be added, google/crc32c.
Some of the changes above are still under development, while others have already landed on master. I hope this information will help you plan adopting the next release.

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Probably just going to mean some GYP config hackery to adapt to the changes they introduce to make it CMake-idiomatic. The C++11 support is easy because Node core is fully C++11 since at least Node 4 and V8 keeps on pushing hard on that front (a little awkwardly in some cases). The google/crc32c dependency will be interesting, we may want to pull that in because I guess it'll add some nice extra error-checking capabilities.

[peakji]

google/crc32c looks great, benchmarks: google/leveldb@5c39524

[pirxpilot]

Somewhat related: I attempted switching to cmake-js to build latest leveldb (master) in my fork. I seems to work OK for MacOS and Linux, I did not try that on other platforms and I am sure I am missing some things that are obvious to people more familiar with the project.

For what it's worth cmake builds seem to be easy: snappy and crc32c already use cmake, which makes our CMakeLists.txt look... uncomplicated (at least compared to what I see in .gyp files). Latest prebuild (and prebuild-install) works with cmake-js as well.

In any case, feel free to pick up any useful stuff.

[vweevers]

I guess now we have to add cmake-js to prebuildify? Like prebuild/prebuildify#7

[vweevers]

A rough description of tasks (feel free to edit):

• Diff our deps/leveldb/leveldb-1.20 against upstream 1.20, generate .patch files (#459)
• Update to 1.22
• Possibly get rid of deps/leveldb/port-libuv, because LevelDB got Windows support
• Apply patches (if still needed)
• Either update leveldb.gyp or switch to cmake-js. I prefer the former atm, because cmake-js is flaky on Windows and we'd have to change and retest our whole prebuild setup.

[rvagg]

Got any details on the cmake-js flaky problems? We've been discussing the future of gyp and node-gyp and cmake-js came up as something that we might encourage as an option but I have no experience with it.
Gyp still has a future, we're taking proper ownership of it in the nodejs org and have a plan for a gradual migration go a gyp.js that will help deal with the massive gyp investment in the ecosystem. So I for leveldown, sticking with gyp is a safe choice if cmake-js bears any risk.

[vweevers]

@rvagg I have no experience as a user of cmake-js, but as a maintainer of prebuild which integrates with cmake-js, I know cmake-js is unable to find MSVS since 5.2.0 (july-ish) (cmake-js/cmake-js#186). That's fixable of course, so perhaps flaky isn't fair.

[braydonf]

In addition of the change from SNAPPY to HAVE_SNAPPY, there is also LEVELDB_IS_BIG_ENDIAN, HAVE_FDATASYNC, HAVE_FULLFSYNC and HAVE_CRC32C.

The patches to LevelDB are likely not necessary anymore, as it's related to LEVELDB_PLATFORM_UV, which can likely be LEVELDB_PLATFORM_WINDOWS now, and defined(OS_IOS) may not be necessary.

Edit: These can be defined in port/port_config.h.